Light always travels at a speed of 299,792,458 meters per second. But if you're in motion too, you're going to perceive it as traveling even faster -- which isn't possible! In this second installment of a three-part series on space-time, CERN scientists Andrew Pontzen and Tom Whyntie use a space-time diagram to analyze the sometimes confounding motion of light.

Austrian physicist Erwin Schrödinger, one of the founders of quantum mechanics, posed this famous question: If you put a cat in a sealed box with a device that has a 50% chance of killing the cat in the next hour, what will be the state of the cat when that time is up?

In episode one, Helen ventures to the bottom of the temperature scale, revealing how cold has shaped the world around us and why frozen doesn't mean what you might think. She meets the scientists pushing temperature to the very limits of cold, where the normal laws of physics break down and a new world of scientific possibility begins. The extraordinary behaviour of matter at temperatures close to absolute zero is driving the advance of technology, from superconductors to quantum computing.

Particle physicist Dr Brian Cox wants to know why the Universe is built the way it is. He believes the answers lie in the force of gravity. But Newton thought gravity was powered by God, and even Einstein failed to completely solve it. Heading out with his film crew on a road trip across the USA, Brian fires lasers at the moon in Texas, goes mad in the desert in Arizona, encounters the bending of space and time at a maximum security military base, tries to detect ripples in our reality in the swamps of Louisiana and searches for hidden dimensions just outside Chicago.

Imagine turning yourself into a crime fighting super hero just like Batman or Iron man. Dr Michio Kaku designs a suit that would give the wearer the super powers of a comic book super hero. Take that bad guys!